Method and device for coding/decoding image using intra prediction

Abstract

A method and a device for encoding/decoding an image according to the present invention may determine a reference region for intra prediction of a current block, derive an intra prediction mode of the current block on the basis of a predetermined MPM candidate group, and perform intra prediction on the current block on the basis of the reference region and the intra prediction mode.

1 . A method of decoding an image, comprising:
 deriving an intra prediction mode of the current chroma block based on a predetermined candidate intra prediction mode group; and   performing the intra prediction on the current chroma block based on the intra prediction mode,   wherein the predetermined candidate intra prediction mode group is divided into a first group and a second group,   wherein the first group includes at least one inter-component prediction mode, and the second group includes an intra prediction mode used for a luma block corresponding to the current chroma block,   wherein the intra prediction mode of the current chroma block is selected by choosing either the first or the second group.   
     
     
         2 . The method of  claim 1 , wherein the first group consists of three (3) inter-component prediction modes. 
     
     
         3 . The method of  claim 1 , further comprising:
 obtaining a first flag from a bitstream, and   wherein the intra prediction mode of the current chroma block is derived from the one of the first group or the second group selected based on the first flag.   
     
     
         4 . The method of  claim 3 , wherein when a value of the first flag is a first value, the intra prediction mode of the current chroma block is derived from the first group based on first index information obtained from the bitstream, and
 wherein when the value of the first flag is a second value, the intra prediction mode of the current chroma block is derived from the second group based on second index information obtained from the bitstream.   
     
     
         5 . The method of  claim 1 , further comprising:
 deriving, in case the intra prediction mode of the current chroma block is the inter-component prediction mode, correlation between a chroma component and a luma component; and   performing inter-component prediction for the current chroma block based on the correlation.   
     
     
         6 . The method of  claim 1 , wherein the deriving correlation comprises deriving a downsampled luma sample using a plurality of luma samples. 
     
     
         7 . A method of encoding an image, comprising:
 deriving an intra prediction mode of the current chroma block based on a predetermined candidate intra prediction mode group; and   performing the intra prediction on the current chroma block based on the intra prediction mode,   wherein the predetermined candidate intra prediction mode group is divided into a first group and a second group,   wherein the first group includes at least one inter-component prediction mode, and the second group includes an intra prediction mode used for a luma block corresponding to the current chroma block,   wherein the intra prediction mode of the current chroma block is selected by choosing either the first or the second group.   
     
     
         8 . A computer-readable recording medium storing a bitstream generated by a method of encoding an image, the method comprising:
 deriving an intra prediction mode of the current chroma block based on a predetermined candidate intra prediction mode group; and   performing the intra prediction on the current chroma block based on the intra prediction mode,   wherein the predetermined candidate intra prediction mode group is divided into a first group and a second group,   wherein the first group includes at least one inter-component prediction mode, and the second group includes an intra prediction mode used for a luma block corresponding to the current chroma block,   wherein the intra prediction mode of the current chroma block is selected by choosing either the first or the second group.